PDF(Pubmed)
Abstract：
Polyphenism is a type of developmental plasticity that translates continuous environmental variability into discontinuous phenotypes. Such discontinuity likely requires a switch between alternative gene-regulatory networks, a principle that has been borne out by mechanisms found to promote morph-specific gene expression. However, whether robustness is required to execute a polyphenism decision has awaited testing at the molecular level. Here, we used a nematode model for polyphenism, Pristionchus pacificus, to identify the molecular regulatory factors that ensure the development of alternative forms. This species has a dimorphism in its adult feeding structures, specifically teeth, which are a morphological novelty that allows predation on other nematodes. Through a forward genetic screen, we determined that a duplicate homolog of the Mediator subunit MDT-15/MED15, P. pacificus MDT-15.1, is necessary for the polyphenism and the robustness of the resulting phenotypes. This transcriptional coregulator, which has a conserved role in metabolic responses to nutritional stress, coordinates these processes with its effects on this diet-induced polyphenism. Moreover, this MED15 homolog genetically interacts with two nuclear receptors, NHR-1 and NHR-40, to achieve dimorphism: Single and double mutants for these three factors result in morphologies that together produce a continuum of forms between the extremes of the polyphenism. In summary, we have identified a molecular regulator that confers discontinuity to a morphological polyphenism, while also identifying a role for MED15 as a plasticity effector.
摘要：
多表型是一种发育可塑性，可将连续的环境变异性转化为不连续的表型。这种不连续性可能需要在替代的基因调控网络之间进行切换，这一原理已被发现促进形态特异性基因表达的机制所证实。然而,是否需要健壮性来执行多表型决策，还在等待分子水平的测试。这里,我们用线虫模型来研究多表型,Pristionchuspacificus,确定确保替代形式发展的分子调节因素。该物种的成年摄食结构具有二态性，特别是牙齿,这是一种形态上的新颖性，可以捕食其他线虫。通过前向基因筛选，我们确定，Mediator亚基MDT-15/MED15的重复同源物P.pacificusMDT-15.1对于所得表型的多表型和稳健性是必需的。这个转录共调节因子，在对营养压力的代谢反应中具有保守的作用，协调这些过程及其对饮食诱导的多表型的影响。此外，这个MED15同系物与两个核受体在基因上相互作用，NHR-1和NHR-40，以实现二态：这三个因素的单突变体和双突变体导致形态，共同在多表型的极端之间产生连续的形式。总之,我们已经确定了一种分子调节剂，它赋予了形态学多表型的不连续性，同时还确定了MED15作为可塑性效应物的作用。
